Method of fabricating a varactor/oscillator diode module for a tunable oscillator

Abstract

In a method of fabrication of a module formed by a semiconductor diode which oscillates in millimeter waves and by a variable-capacitance diode, the oscillating diode is mounted on a pedestal at the center of a support base. A ring of fused silica for supporting a metallic disk of predetermined diameter serves to form a radial space between two metallic surfaces with a view to readily obtaining oscillation in a predetermined frequency band. A similar ring is welded at one end to the opposite face of the disk and at the other end to another metallic base fitted with a central variable-capacitance diode. Flexible connections bonded to the diodes are clamped between the rings and the disk. The module may be incorporated in a tunable oscillator.

What is claimed is: 
     
       1. A method of fabricating a module having an oscillator diode and a varactor diode mounted in series, said method comprising the steps of: (A) mounting one of the diodes by welding one of its anode and cathode on a first metallic base which performs the function of a thermal radiator and of a electrode of the module, and thus forming a first subassembly;   (B) mounting the other diode by welding one of its anode and cathode on a second metallic base which performs the function of a second electrode of the module, and thus forming a second subassembly;   (C) equipping each subassembly with a dielectric ring having a first flat face welded to the respective base, said ring surrounding the respective diode so as to provide a second flat face parallel to said first face and forming together with the base surface delimited by the ring and internal walls of said ring, a cylinder which entirely contains the respective diode;   (D) bonding flexible connection so as to connect the other one of said anode and cathode which has remained free in each diode to the second flat face of the respective ring; and   (E) mounting the two subassemblies so that the same face each other with their flat faces bonded to the flexible connections, and welding the same to a third electrode of the module, said third electrode being formed by a metallic disk having a diameter of a size so as to readily obtain oscillation of the oscillator diode at a predetermined frequency.   
     
     
       2. A fabrication method according to claim 1, including, prior to step (A), depositing a metallic later having the function of a thermal radiator on one of the electrodes of the oscillator diode. 
     
     
       3. A method according to claim 1 wherein, both in step (A) and in step (B), a brazing preform is interposed beforehand between the metallic base and the diode. 
     
     
       4. A method according to claim 1 wherein, in step (C), the rings are formed by tube sections of fused silica. 
     
     
       5. A method according to claim 1 wherein, in step (D), flexible connections are utilized in the form of sixarm star connectors. 
     
     
       6. A tunable oscillator incorporating a module comprising an oscillator diode and a varactor diode mounted in series, wherein the module comprises: one of said diodes having one of its anode and cathode welded on a first metallic base which performs the function of a thermal radiator,   the other of said diodes having one of its anode and cathode welded on a second metallic base,   a metallic disk placed between the two diodes, parallel to the first and second metallic base and connecting the two diodes in series with the help of flexible connections,   two dielectric rings, each ring being placed between the metallic disk and one of the metallic bases in order to enclose the respective diode,   said tunable oscillator comprising a cavity provided with three openings through which are introduced respectively the module with the help of its first metallic base, a first biasing rod placed in contact with the metallic disk, and a second biasing rod placed in contact with the second metallic base.   
     
     
       7. A tunable oscillator according to claim 6, wherein the first metallic base is connected to the ground formed by the cavity walls and wherein the biasing rods are isolated from the ground by elements of a material which absorbs electromagnetic waves.